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Describe the difference between the alimentary canal (GI Tract) and the accessory organs:
Alimentary Canal:
Tube food passes through
Digests and absorbs
Accessory Organs:
Structures (organs , glands) aid in digestion
List the regions of the GI tract and the accessory organs of the digestive system:
GI tract
Mouth, Pharynx, Esophagus, Stomach, Small Intestines, Large Intestines
Accessory Organs
Teeth, Tongue, Salivary Glands, Pancreas, Liver, Gall Bladder
Distinguish between mechanical and chemical digestion:
Mechanical- Physical Breakdown
Chemical- Enzymatic breakdown into smaller compounds
Identify the four layers of the wall of the digestive tract and their basic functions:
Muscosa- Epithelial Lining
Submucosa- CT Layer
Muscular Externa- Muscle Layer
Serosa- Covering
Differentiate between peristalsis and segmentation:
Peristalsis- Moves material through gut
Segmentation- Helps mix material with digestive enzymes in small intestine
Describe the general neural and hormonal controls over digestive function:
Enteric Nervous System:
Enteric neurons control GI muscle contraction
Control smooth muscles and glands
Receive CNS motor input from ANS:
Parasympathetic - Increase GI activity
“Rest and Digest”
Sympathetic - Decrease GI activity
“Fight or Flight”
Describe the gross anatomy of digestive tract from the mouth through the esophagus:
-Mouth: site for chewing, bolus created and pushed back into pharyx
-Pharynx: muscular funnel that connects oral cavity to esophagus
-Esophagus: muscular tube that carries food into stomach
Describe the muscular control as food moves from the mouth to the esophagus and towards the stomach:
Waves of muscle contractions called peristalsis force food down through the esophagus to the stomach. A person usually isn't aware of the muscle movements that push food through the digestive tract. The stomach: At the end of the esophagus is a muscular ring or valve called a sphincter
Describe the composition and functions of the components of saliva:
Salivary Glands Two groups:
Intrinsic – buccal glands
Extrinsic (3 pairs)
1. Parotid glands 2. Sublingual glands 3. Submandibular glands.
Salivary Proteins
Mucin - Lubricating glycoprotein
Lysozyme - Bacteriostatic enzyme
IgA = Abs
Defensins - Antibiotic/chemotactic neutrophil secretion
Salivary amylase - Hydrolyzes starch
Describe the neural control of salivation
ANS Control
Sympathetic - ↓ salivation
Parasympathetic - ↑ salivation
Psychological Control - Response to visual/olfactory stimuli
Can be stimulated by lower GI irritation
Explain the extent to which digestion/absorption occurs in the mouth through the esophagus.
Digestion/Absorption – Mouth to Esophagus
* Ingestion
* Mechanical digestion - Mastication by teeth. - Formation of bolus.
* Chemical digestion - Salivary amylase breaks down starch/glycogen
* Deglutition (swallowing) then peristalsis
- Voluntary (mouth)
⇒ reflexive (pharynx)
⇒ involuntary (end of esophagus – smooth muscle)
* Absorption = NONE (except some drugs) e.g. nitroglycerin
Contrast the structure of the gastric mucosa with that of the esophagus.
Mucosa – stratified squamous epithelium
Submucosa – mucus-secreting esophageal glands
Muscularis – skeletal ⇒ smooth
Describe the gross and microscopic anatomy of the stomach.
Cardiac region
Cardiac sphincter
Fundus
Body
Greater & lesser curvatures
Pyloric region
Pyloric sphincter
Describe how the muscularis of the stomach differs from that of the rest of the GI tract.
Unique qualities
Simple columnar epithelial mucosa ⇒ In folds called rugae
3-layer muscularis
3 sections
1. Surface epithelium
2. Gastric pits
3. Gastric glands ⇒ Secretes gastric juice
List the four types of epithelial cells in the pits of the gastric mucosa.
Mucus neck cells ⇒ Bicarbonate-rich mucus
Parietal cells ⇒ HCl
Chief cells ⇒ Pepsinogen (inactive form of protease pepsin)
Enteroendocrine cells ⇒ Release hormones carried to digestive organs by the blood
Identify the secretions of these cells and state their functions.
Enteroendocrine Cell Products
Gastrin – MOST IMPPORTANT ⇒ ↑ gastric cell activity, gastric emptying, contraction of SI & LI, ileocecal valve relaxation.
Histamine - ↑ H + secretion
Endorphins – kill pain
Serotonin - ↑ contraction of stomach SM
Somatostatin (also secreted by SI) ⇒ Inhibits stomach, pancreas, SI, gall bladder.
Explain the extent to which digestion/absorption occurs in the stomach
Mechanical Digestion ⇒ Mixing waves
Chemical Digestion ⇒ HCl (parietal cells) activates pepsin (chief cells) which becomes protease (breaks down protein
Movement ⇒ Peristalsis into SI
Absorption ⇒ Only lipid-soluble substances. E.g. aspirin, alcohol
Describe the three modes by which gastric activity is regulated (activated/inhibited)
Hormones ⇒ Gastrin (increases) vs. somatostatin (inhibits)
Neural Control
⇒ ANS - Parasympathetic increases. - Sympathetic decreases
Local enteric nerve
⇒ Distension of stomach activates stretch receptors. - Stimulates stomach.
⇒ Distension of SI (duodenum) - Inhibits stomach
Contrast cephalic, gastric, and intestinal regulation of the stomach.
Cephalic Regulation of Stomach
Stimulation of stomach
Think food
⇒ See, taste, smell, etc.
⇒ Vagus nerve of PS ANS increases activity
Inhibition of stomach
Think otherwise
⇒ ↓ appetite & depression decreases PS ANS
⇒ Emotional upset increases S ANS
Gastric:
Gastric Regulation of Stomach
Stimulation of stomach
Stomach distension ↑ PS ANS
↑ pH (caffeine/ peptides)
Inhibition of stomach
No stomach distension
↓ pH
Intestinal:
Intestinal Regulation of Stomach
Stimulation of stomach
Slight drop in pH & partially-digested food in duodenum ⇒ Secretes gastrin
Inhibition of stomach
Duodenum distension; fatty, acidic, hypertonic chyme
* Enterogastric reflex
⇒ Inhibits PS ANS (Vagus)
⇒ Activates S ANS (closes pyloric sphincter)
* Inhibitory intestinal hormones (example: somatostatin)
Differentiate among the following gastric conditions: gastritis and gastric ulcers.
Gastritis
Inflammation of underlying layers of wall
Gastric ulcers
Erosion of stomach wall
Helicobacter pylori associated with 80-90% of ulcers
Describe emesis
Emesis = vomiting
Caused by:
⇒ Extreme stretching of stomach/SI
⇒ Irritants (bacterial toxins, excessive alcohol, spicy foods, some drugs)
Emetic center:
⇒ Increases abdominal pressure
⇒ Relaxes cardiac sphincter
⇒ Raises soft palate (closes nasal passages)
Describe the gross and microscopic anatomy of the small intestine.
Functions:
⇒ Secretion (proximal end)
⇒ MOST digestion & absorption of all GI tract
Three areas
⇒ Duodenum – receives chyme
- Duodenal glands (alkaline mucous)
- Hepatopancreatic sphincter (fluids from liver/pancreas)
⇒ Jejunum – duodenum to ileum
⇒ Ileum – jejunum to LI (through ileocecal valve)
State how the structure and function of the mucosa of the small intestine differs from that of the stomach.
Circular folds
- Forces spiral movement of chyme ⇒ Slows movements for ↑ absorption
Villi = Fingerlike projections of mucosa ⇒ Contain capillaries & lacteal
Microvilli = Cell membrane projections
Brush border secretes enzymes
Increases surface area (SA)
Describe how each major class of nutrients is chemically digested.
Describe how each major class of nutrients is chemically digested.
Chemical Digestion
By hydrolysis of macromolecules
Digests (pancreatic enzymes):
⇒ Lipase - lipids
⇒ Proteases - Large peptides → small peptides → AAs
⇒ Amylase - Starches → disaccharides → monosaccharides
⇒ Nucleases (also nucleosidases & phosphotases) - NAs → nucleotides → sugars, phosphates,bases
Name the substrates (major organic macromolecules), enzymes, and products of digestion.
Digests (pancreatic enzymes):
⇒ Lipase - lipids
⇒ Proteases - Large peptides → small peptides → AAs
⇒ Amylase - Starches → disaccharides → monosaccharides
⇒ Nucleases (also nucleosidases & phosphotases) - NAs → nucleotides →
sugars, phosphates,bases
Describe how each type of nutrient is absorbed by the small intestine.
Nutrients/vitamins move from lumen across cells and into blood/lymph
Nutrient monomers absorbed
⇒ Carbohydrates: monosaccharides into blood
⇒ Proteins: AAs into blood
⇒ Lipids: into lymph
⇒ Nucleic acids: ribose, phosphate, & bases into blood
Vitamins
⇒ Fat soluble into lymph - A, D, E & K
⇒ Water soluble into blood - B & C
Describe the hormonal/neural control of the small intestine.
Hormones
Gastrin - ↑ SM contraction & ileocecal valve relaxation
Vasoactive intestinal peptide (VIP) - ↑ bicarbonate-rich intestinal juices
Neural Control
⇒ PS ANS increases activity
⇒ S ANS decreases activity
Describe the condition known as Celiac disease.
A chronic digestive and immune disorder that damages the small intestine.
Describe the digestive secretions and functions of the pancreas, liver, and gallbladder.
Liver
Largest gland in body
⇒ Produces bile
⇒ Joins cystic duct from gall bladder to form bile duct
Gall bladder - Stores bile
Pancreas
⇒ Secretes digestive enzymes
⇒ Pancreatic duct joins bile duct
Explain how hormones regulate secretions of the pancreas, the liver, and the gall bladder.
Acidic, fatty chyme causes production of
1. Secretin
⇒ Stimulates bile production by liver
⇒ Stimulates secretion of bicarbonate pancreatic juices
2. Cholecystokinin
⇒ Stimulates gall bladder contraction
3. Acetylcholine
⇒ Stimulates secretion of pancreatic enzymes
Differentiate among the following disorders/conditions: hepatitis, cirrhosis, jaundice, and gallstones.
Hepatitis
⇒ Inflammation caused by viral infection
⇒ Transmitted enterically or through blood
Cirrhosis
⇒ Chronic disease & growth of scar tissue
Jaundice
⇒ Yellowing of the skin through buildup of bilirubin from liver disease OR high RBC destruction
Gallstones
⇒ Crystallization of cholesterol due to excess
Obstructive jaundice
⇒ Yellow skin due to bile duct blockage
Describe the gross and microscopic anatomy of the large intestine.
Cecum ⇒ Including vermiform appendix
Colon
Ascending
Transverse
Descending
Sigmoid
Rectum
Anal canal ⇒ Anal sphincter
Contrast the mucosa of the colon with that of the small intestine.
Mucosa
Simple columnar with many goblet cells
Anal canal
⇒ Stratified squamous epithelium
⇒ Anal sinuses secrete mucus
Submucosa
Thinner than in SI
State the physiological significance of intestinal bacteria.
⇒ Resident bacteria dominated by Escherichia coli (E. coli)
⇒ Ferment some indigestible carbohydrates
- Results in mixture of acids and gases
⇒ Synthesizes vitamins B & K
Explain the neurological control of defecation.
- Parasympathetic reflex relaxation of internal anal sphincter (smooth muscle)
- Voluntary control over relaxation of external sphincter (skeletal muscle)
Differentiate among the following disorders/conditions: diarrhea, constipation, hemorrhoids, and appendicitis.
Diarrhea
⇒ Watery stools due to shortened time in LI
⇒ Loss of water leading to dehydration
Constipation
⇒ Hard stools due to longer time in LI
Hemorrhoids
⇒ Inflammation of superficial perianal veins
Appendicitis
⇒ Infection of appendix
List the general functions of the urinary system:
Maintain blood composition and volume:
Regulating water content
Maintaining ionic concentrations
Mainting pH balance
Removing metabolic wastes (urea)
Other functions:
Secretes renin (affects blood pressure)
Secretes erythropoietin (affects RBC formation)
Identify the microscopic anatomy of the urinary system:
Kidneys (Upper lumbar region)
Ureters (Extend from kidney to urinary bladder)
Urinary Bladder (In pelvic cavity; stores urine)
Urethra (Extends from bladder to urethra)
Identify the microscopic anatomy of a nephron:
Afferent and Efferent Arterioles
Glomerulus
Glomerular Capsule
Proximal Convoluted Tubules
Nephron Loop
Distal Convoluted Tubules
Collecting Duct
List the relevant vessels of the renal circulation as they lead to and from the nephron:
Renal Artery and Vein
Afferent and Efferent Arterioles
Supply blood in and out of the glomerulus to proceed throughout the nephron
Explain the glomerulus and recta/peritubular capillaries:
Blood enters nephrons, a million tiny filtering units found in each kidney. The peritubular capillaries move the blood through the nephrons into filters called the glomerulus. These filters trap fluid, small molecules, and waste in the tubule. Blood cells and proteins pass through the glomerulus harmlessly.
Describe the process by which the kidney filters the blood plasma:
Glomerular filtration is the first step in making urine. It is the process that your kidneys use to filter excess fluid and waste products out of the blood into the urine collecting tubules of the kidney, so they may be eliminated from your body.
Explain the pressures that promote and oppose filtration within the glomerulus:
Difference between pressures forcing fluids into capsular space and pressures resisting filtration
Hydrostatic pressure within the glomerular capillaries promotes or enhances filtration. The other two forces oppose filtration and are: back pressure from hydrostatic pressure of the fluid within the capsule and colloid osmotic pressure caused by the plasma proteins within the glomerular capillaries.
Distinguish between the cells of the juxtaglomerular apparatus (JG)cells and the macula dense (MD) cells:
JG cells:
Smooth muscle in afferent and efferent walls
Respond to low BP by secreting renin
MD cells:
Osmoreceptors
Detect solute concentration in Distal Convoluted Tubule.
Secretes local vasoconstrictor to decrease flow into glomerulus when filtrate concentration is high
Describe the intrinsic and extrinsic controls over glomerular filtration rate:
Intrinsic:
Autoregulation
Kidney controls local blood flow on its own
Stretch response (Afferent arterioles contract during high BP and relax during low BP)
Feedback Mechanism:
Higher BP
Higher filtration rates
High filtration concentration in the DCT
MD cells in the DCT secrete more (vasoconstrictor)
Describe the intrinsic and extrinsic controls over glomerular filtration rate:
Extrinsic:
Sympathetic ANS modulated
Rapid control
Very low BP
Vasoconstriction = increase BP
Afferent arterioles also constrict:
Less blood entered glomerulus
Lower hydrostatic pressure
Decreases filtration rate
Less filtrate (urine) produced
Less loss of fluids
Maintain blood volume and blood pressure
Describe how the nervous system, hormones (renin), and the nephron itself play roles in extrinsic and intrinsic filtration rate:
Hormones: reduces glomerular filtration function, decrease in renal blood flow
Nervous system: Parasympathetic and Sympathetic control (controls digestive activities)
Nephron: the glomerulus filters your blood, and the tubule returns needed substances to your blood and removes wastes.
Explain how these controls can affect blood pressure:
Extrinsic tries to help increase blood pressure and vasoconstriction when BP is low.
Intrinsic helps when BP is too high and vasodilates to help filtration of blood flow and helps lower BP.
Differentiate between tubular reabsorption and secretion:
Reabsorption
Filtrate → Interstitial Fluid → Blood
Nutrients (Sugars, AA’s, Vitamins)
Ions (Regulated by hormones and pH balance)
Water (Antidiuretic hormone)
Differentiate between tubular reabsorption and secretion:
Secretion
Blood → Interstitial Fluid → Filtrate
Wastes (Urea and Acids)
Drugs (Aspirin, Penicillin, Morphine)
Ions (Excess potassium, Hydrogen and Bicarbonate)
List the solutes commonly reabsorbed or secreted by the tubules of the nephron:
Reabsorbed: water salt
Secreted: Organic acids/bases, Potassium and Hydrogen,
Describe the normal composition and properties of urine as a result:
Normal:
Substances partially reabsorbed: Water and Salt
Substances secreted into filtrate: Organic Acids/Bases, Potassium and Hydrogen (Creatinine)
(Volume, Transparency, Color, Odor)
Explain how the collecting duct and antidiuretic hormone regulate the volume and concentration of urine:
Process:
Hypothalamus detects an increase in blood solute concentration
Posterior pituitary secretes ADH
Increase ADH signals water pores to form collecting ducts
DCT and CD increase water permeability
Causes reabsorption of water
(Increase Blood Volume = Increase Blood Pressure)
Explain how the kidney maintains an osmotic gradient in the renal medulla that enables the collecting duct to function:
Physical draw by the solutes on the more concentrated side of the capillary walls
Pulling fluids into the blood (Absorption Force)
Describe three mechanisms by which diuresis can occur:
Condition that inhibit ADH release (Alcohol/Caffeine)
Chemicals that Inhibit Sodium reabsorption (Caffeine)
Any solute that exceeds its transport maximum (Diabetes)
Describe how the structure of the waller of urerters, bladder, and urethra differ in composition and function:
Ureters
- Mucosa - Transitional epithelium (allows stretching)
- Muscularis - Smooth muscle (propels urine by peristalsis)
Urinary Bladder
- Located in pelvic region
- Function: temporary storage of urine
- Designed to withstand stretching
- Mucosa - Transitional epithelium
- Muscularis - Smooth muscle
Urethra
- Duct from urinary bladder to outside
- Internal urethral sphincter
- SM under ANS control
- Urethra - Mucosa - Transitional stratified squamous
- External urethral sphincter - Skeletal muscle under voluntary control
Explain how the nervous system and urethral sphincters control urination:
Duct from urinary bladder to outside
Internal urethral sphincter
SM under ANS control
Urethra
Mucosa (Transitional Stratified Squamous)
External Urethral Sphincter
Skeletal muscle under voluntary control
Differentiate among the following disorders / conditions: incontience, bladder infection/UTI and renal calculi
Incontinence
Inability to control micturition voluntarily
Bladder Infection (UTI)
Invasion of bladder by bacteria
Renal Calculi (Kidney Stones)
Crystallization of calcium, magnesium or uric acid salts in renal pelvis